Sealing apparatus



Nov. 26, 1963 P. P. SPOLSINO 3,111,794

SEALING APPARATUS Filed Dec. 29. l9 61 I iiiliiiinm ME 3 A lun'flllfllllllllll 11 lll lllllm United States Patent 3,111,794 dErtLlNG APPARATUS Peter P. Spolsino, Revere, Mass, assignor to W. R. Graee & (10., Cambridge, Mass, a corporation of Qonnectieut Filed Dec. 29, 1961, Ser- No. 163,163 7 Claims. Cl. 53-14) This invention relates to bag sealing and more particularly, to an apparatus and a method for sealing the gathered end of a thermoplastic bag so as to obtain an air tight seal.

A common method of sealing the open end of thermoplastic bags requires that opposite sides of the open mouth be brought together and that sufficient heat be applied to the thermoplastic material to fuse the two sides to gether. This necessarily results in a rather wide closure extending the width of the package which, while suitable for packaging some products, is equally unsuitable for others. For example, when packaging whole poultry or primal meat cuts, it is preferred that the bag, including the sealed area, closely conform to the product. Conventional heat sealing, therefore, produces seals that lie some distance from the end of the product and are relatively straight, loose fitting seals.

Another method of closing bags and one that permits the sealed area to more closely conform to the product involves the application of a deformable metal band about the gathered end of the bag. The clip can be applied to the gathered end of the bag in close proximity to the bagged product. With the development of clip applying devices and suitable clips, it is now possible with this method to quickly obtain reliable seals. Several problems exist in connection with clip sealing, the most serious of which is the difficulty in obtaining an air tight closure. The gathered neck of the bag about which the clip is applied has a myriad of channels created by the folding of the bag through which air can pass into the interior of the bag. To close off these channels, it is necessary to apply the clips tightly around the gathered neck of the bag. Because the bags of thermoplastic material are relatively fragile, the use of sufiicient pressure to close the air passages is likely to cause the clip to tear into the bagdestroying the integrity of the closure. The problem is even more serious with large bags, since correspondingly greater pressures must be applied to seal the bag.

The problem of obtaining unobtrusive, small conforming seals is not completely solved by the clip crimping technique where it is desired to obtain air tight closures on all bag sizes. While it would theoretically be possible to heat fuse the gathered neck of a thermoplastic bag, this is not practical, since the fused material must be held under restraint or otherwise supported while the material is cooling and solidifying. A not inconsiderable length of time must elapse before the seal acquires any strength. The time required to cool the fused thick mass of material to a point where the heat seal will become self-supporting has proven to be of such long duration that it is not considered economically practical to seal bags in this manner.

It is an object of the present invention to obtain an air tight seal on thermoplastic bags of any size, which seal will be relatively small and conform to the product. It is a further object to provide apparatus which will quickly and positively produce an air tight seal.

Other objects and advantages of the present invention will become apparent with the following detailed description of the invention taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a side view of the apparatus of the present invention in perspective and partially in section;

FIGURE 2 is a front view of the apparatus of FIG- URE l in perspective;

FIGURE 3 is a partial front view of the apparatus in perspective;

FIGURE 4 is a partial view of the clipped and fusesealed bag end; and

FIGURE 5 is a partial view of the fused bag end without the clip.

This invention, then, comprises a method and an apparatus suitable for carrying out the method, which pro duces an air tight seal in the open end of a thermoplastic bag. As an example, a primal cut of meat (e.g., a beef round) is inserted in a 30-inch wide, 2 /2 mil thick saran (vinylidene chloride copolymer) bag. The open end of the bag is gathered and preferably, though not necessarily, twisted, and a clip is crimped about the gathered or twisted portion. The neck of the bag extending beyond the clip is then severed so that a very short length-e.g., of an inchof bag material extends beyond the clip. This portion of bag material extending beyond the clip is then heated above its fusion temperature. The heated portion of the neck fuses into a solid mass which effectively seals the end of the bag. The bag may be removed without waiting for the fused area to cool and harden, since the clip will mechanically support or hold the gathered neck of the bag. Ultimately, the seal strength will reach a point where it will no longer be necessary to rely on the support of the clip and in fact, if desired, the clip could be removed without any loss of strength in the sealed area.

The preferred embodiment of the apparatus of the present invention comprises a base plate it) which may be placed upon and fastened to a suitable work surface (not shown) and a support member 11 extending upwardly from and mounted on said base plate. A clip crimping bed, designated generally as 12, which functions to hold a clip and to form it around the gathered bag neck, extends upwardly from said base plate 10 and is attached to said support member 11.

A slot-like opening 13 extends through the top and nearly to the bottom of said clip crimping bed 12. A recessed guide channel 14 is located in the side wall of the bed defining the opening 13. The channel 14 forms a smooth curve near the base of the bed. This curved section 15 forms the anvil of the clip crimping bed. One side wall 16 of the bed is secured to the support frame 11. The other side wall 17 is also fastened at 17' to the support frame and has a section broken away. A swing plate 13 is pivotally attached to the side wall 17 above the break at point 19 and in the down position functions to close the side wall 17 and in the up or open position breaks open the side wall of the bed. A suitable handle is positioned on the swing plate 18 to facilitate movement to and from the open and closed positions.

A single acting, pneumatic cylinder 20 mounted on the support frame 11 and positioned above the clip crimping bed, drives a ram 21 downward within the slot-like opening 13. A spring return (not shown) retracts the ram from its fully extended position when the air pres sure is reduced in the cylinder. Air pressure to operate the cylinder 20 is carried via tubing 20 from a suitable source of compressed air (not shown).

An upward extension 22 of the support frame 11 funca tions as a clip feeder. The clips 23 are inverted, U-shaped bands formed of a ductile metal, e.g., aluminum. The extension 22 is an upright, U-shaped channel that holds a plurality of clips and gravity feeds the clips to the clip crimping assembly. The leading clip is gravity fed into position in the opening 113 at the top of the clip crimping bed 12 where it is held in place by frictional engagement with the channel walls. Sections of the channel wall closest to the clips are removed so that the clip will slip into the channel lid. The channel walls are wide enough to accommodate a single clip. The wall 26 of the swing plate 18 is also channeled so that when the swing plate is in the down or closed position, the channel is continuous.

As the ram 21 is driven downwardly by the pneumatic cylinder 2%, it contacts the base 25 of the clip 23 and pushes the clip down the slot-like opening 13. The two downwardly extending side arms 26 of the clip are located within the channel 14 on either side of the opening 13. The clip is pushed downward until it reaches the curved portion comprising the anvil 15. At this point, the two side arms 26 of the clip are forced to bend toward each other as they conform to the curve of the anvil. This bending continues until the ends of the two arms come into contact with each other closing the clip.

A pair of knife blades, comprising an upper movable blade 31 and a lower fixed blade 32, are located just forward of the clip crimping bed 12. The lower knife blade is mounted on a knife swing plate 39. A shaft 33, fixedly attached to the side of the knife swing plate 3th, is supported by a lower bearing 34 and an upper bearing 35. Both bearings 34- and 35 are mounted on the support member 11 and permit rotary movement of the shaft 33.

The upper movable knife blade 31 is carried by a movable knife arm 36. A guide rod 57, extending upwardly from the knife swing plate Sit, passes through a guide opening in the knife arm. A sliding bar 38 is rigidly attached to the knife arm as, and extends downwardly and passes through a guide opening 3@ which projects outwardly from the knife swing plate. A piston rod 4t), driven by a double acting air cylinder 41 which cylinder is mounted on the top of the knife swing plate, is connected to the knife arm as. A downward stroke of the piston rod ill pushes the knife arm 36 until the upper blade 31 contacts the lower fixed blade 32. The path of the knife arm is determined by the guide rod 37 and the sliding bar 38. An upward stroke of the piston rod draws the knife arm upwardly, separating the knife blades.

The knife blades 31 and 32 are continuously heated by a small electrical heating element embedded in each blade. Separate variable resistor controls are connected in the circuit of each heating element permitting accurate control of the temperature of each knife blade. The heated blades remain in contact with the severed edge of the thermoplastic bag and heat said edge until fusion of the plastic material occurs.

A swing arm as is rigidly fixed at one end 61 to the top of shaft 33. The opposite end terminates in a clevis lug 42. One end of a piston rod 44 is connected to the clevis lug by a pin and the opposite end of the piston rod is connected to the piston of a double acting air cylinder 45 mounted on the support member 11. As the air cylinder draws the piston rod into the cylinder that end of the swing arm connected to the piston rod is pulled toward the cylinder. The movement of the swing arm results in a rotary movement being applied to the shaft 33 and to the knife swing plate 3%. Drawing the piston rod 44 into the cylinder 45 results in the two knife blades being swung in an arc towards the clip crimping bed 12. The action of the cylinder in extending the rod 4-4 has the effect of moving the knife blades away from the clip crimping bed. It can be observed in FIGURE 2 that the knife blades in their cutting position cut the gathered film neck about A of an inch away from the clip and at a slight angle with respect to the clip crimping bed. The knife blades which are still closed are then forced against the cut end of the film neck, applying heat and pressure. It is necessary to apply pressure as well as heat to the severed edge to compress the fused mass and to hold the heated surfaces against the thermoplastic material. While this is going on, the ram is still in the down position pressing the clip about the neck and preventing any rearward movement of the neck away from the knife blades as they bring pressure to bear on the cut edge.

Operation The knife blades are heated to and maintained at a temperature ranging from 500 F. to 575 F., which range has been found suitable for fusing saran-type films during the three to four second interval that the blades contact the films. The upper knife blade 31 is in the up or open position and the knife swing plate 3t is in an open positi0ni.e., swung away from the clip crimping bed 12. The open end of a therm0plastic-e.g., Saran-bag is gathered, and the gathered neck is placed on the anvil 15 of the clip crimping bed.

The swing plate 13 is swung downward into the closed position by the operator. A connecting rod 46 pivotally mounted at l? to the swing plate 18, is connected at 48 to a valve arm 5%. The downward movement of the connecting rod as it follows the swing plate, pushes the valve arm, opening an air valve (not shown) which allows the compressed air to enter the single acting pneumatic cylinder 2%. The cylinder it) drives the ram 21 downward engaging clip 23 and pushing the latter down the guide channel 14. When the clip reaches the curved portion of the anvil 15, the arms 26 are forced to bend toward each other conforming to the curve of the anvil. The leading edge of the arm come in contact and the ram flattens the clip about the neck of the bag.

Closing the swing plate, trips a micro-switch 55 which starts a first timer. At the expiration of 0.5 second, the first timer energizes a second timer and also actuates the air cylinder 41 causing the upper knife arm 36 and the upper knife blade 31 to be driven downward, cutting off the excess bag neck beyond the clip.

Approximately three seconds after the second timer has been started, it trips a third timer and simultaneously energizes the air cylinder 45 which, acting through the swing arm 5%, turns the knife swing plate against the cut end of the bag neck applying sufiicient pressure to insure a good fuse seal.

The third timer has a one to two second cycle at the expiration of which it actuates cylinders 41 and 45, causing the upper knife blade to return to the open position and causing the knife swing plate to swing away from the cut fused end of the neck. At this point, the operator releases the swing plate and a tension spring 51 draws the swing plate into open position. The connecting rod acting through the valve arm closes the valve leading to the supply of compressed air and opens an air escape valve in the cylinder so that the spring return will lift the piston and the ram. The fuse sealed package is removed from the anvil of the climp crimping bed.

Sources of compressed air, means for energizing the double acting air cylinders, heating elements for the knife blades, as well as the circuits involved in the various timing mechanisms are all conventional and well-known to the prior art, and therefore, it is unnecessary to give a detailed description thereof in the present application.

The fused sealed bag produced in the manner heretofore described is shown in detail in FIGURE 4 and in FiGURE 5 with the clip 23 removed. The solid fused mass 52 extends back from the edge approximately of an inch.

it is obvious that other thermoplastic materials may be similarly fuse sealed, e.g., polyethylene, polypropylene, polyvinyl chloride, etc.

The invention described in detail in the foregoing specification is susceptible to changes and modification as may occur to persons skilled in the art without departing from the principle and spirit thereof. The terminology used is for purposes of description and not of limitation, the scope of the invention being defined in the claims.

I claim: 1

1. Apparatus for sealing the open end of a thermoplastic bag comprising:

(a) means to apply a clip tightly around the gathered neck of the bag,

([2) severing means adjacent to said clip applying means adapted so as to sever the excess neck of the bag at a point a short distance from the clip,

() means to heat the severed edge of the bag neck above its fusion temperature, and

(d) pressure means to urge said heating means towards the clip applying means and against the severed edge, said heating and pressure means cooperating to fuse the severed neck of the bag.

2. Apparatus for sealing the open end of a thermoplastic bag comprising:

(a) means to apply a clip tightly around the gathered neck of the bag,

([1) severing means, adjacent to said clip applying means, adapted so as to sever the excess neck of the bag at a point a short distance from the clip,

(0) heating means located in said severing means and adapted to heat the severed edge of the bag above its fusion temperature, and i (d) pressure means urging said heated cutting means towards the clip applying means and against the severed edge, said pressure means and said heated cutting means cooperating to fuse the severed neck of the bag.

3. Apparatus for sealing the open end of a thermoplastic bag comprising:

(a) means to apply a clip tightly around the gathered neck of the bag,

(11) a pair of opposed heated cutting surfaces positioned adjacent to said clip applying means,

(c) a first means operable to drive said cutting surfaces together in cutting relationship so as to sever the neck of the bag a short distance removed from the clip, and

(d) a second means operable to force said heated cutting surfaces towards the clip applying means and against said severed neck whereby said heated cutting surface is caused to fuse the severed neck of the bag.

4. A method of sealing the open end of a thermoplastic bag which comprises:

(a) tightly crimping a clip around the gathered neck of the bag,

(b) severing the excess of the neck of the bag a short distance from the clip, 1

(c) heating the unsevered neck above its fusion temperature, and

(d) comprmsing the heated thermoplastic edge towards the clip to form a compact fused mass.

5. Apparatus for sealing the open end of a thermoplastic bag comprising:

(a) a stationary clip crimping bed;

(b) a clip feed and clip crimping means co-operating with said bed;

(0) a swing plate located adjacent to but spaced from said crimping bed;

(d) a first knife blade fixedly secured to said swing plate;

(e) a second knife blade mounted for reciprocal movement into cooperative cutting relationship with the first knife blade;

(f) means for heating each of the knife blades;

(g) means for rotating said swing plate in an arc towards said clip crimping bed while the heated knife blades remain in closed cutting relationship.

6. Apparatus of claim 5 further comprising:

(a) power means for motivating said clip crimping means; I

(b) power means for reciprocating the second knife blade; and

(c) power means motivating said rotating means.

7. Method for sealing the open end of a thermoplastic bag comprising:

(a) gathering the open end into a neck;

(12) tightly crimping a clip around the gathered neck;

(0) holding the clip in a stationary position;

(d) severing the excess of the neck of the bag a short distance from the clip;

(e) heating the rmsevered neck portion above its fusion temperature; and

(f) axially compressing the hot fused neck portion towards the clip to form a compact fused mass.

References Cited in the file of this patent UNITED STATES PATENTS 2,071,300 Giammeter Feb. 16, 1937 2,513,459 Dodge July 4, 1950 2,656,658 Grady Oct. 27, 1953 2,781,900 Snyder et al Feb. 19, 1957 2,831,302 Jensen et a1 Apr. 22, 1958 3,041,801 Harrison July 3, 1962 

4. A METHOD OF SEALING THE OPEN END OF A THERMOPLASTIC BAG WHICH COMPRISES: (A) TIGHTLY CRIMPING A CLIP AROUND THE GATHERED NECK OF THE BAG, (B) SEVERING THE EXCESS OF THE NECK OF THE BAG A SHORT DISTANCE FROM THE CLIP, (C) HEATING THE UNSEVERED NECK ABOVE ITS FUSION TEMPERATURE, AND (D) COMPRESSING THE HEATED THERMOPLASTIC EDGE TOWARDS THE CLIP TO FORM A COMPACT FUSED MASS. 